The present invention generally relates to environmental control systems (ECSs) and air cycle cooling systems (ACCSs). More specifically, the present invention relates to an improved ACCS and improved method of conditioning water vapor compressed air and recovering wasted energy from a liquid load, while reducing the system size and improving water removal efficiency.
ACCSs are used to provide a supply of conditioned air to an enclosure, such as an aircraft cabin and cockpit. In the past, ACCSs have utilized an air-to-air cycle cooling system with an integrated liquid loop. But the liquid loop has been primarily for the purpose of cooling radar or other avionics, not for the air to be conditioned. In such systems, a flow of bleed air is taken from an intermediate or high pressure stage within a jet engine having multi-compression stages. The bleed air has usually been pre-cooled within a primary heat exchanger with heat being rejected to RAM air and then flowed to a compressor. After compression, the air has been routed through a secondary heat exchanger. Next, the air is typically flowed into an air-to-air reheater heat exchanger and then to an air-to-air condenser heat exchanger. Condensed water vapor is extracted by a water extractor, and then routed and evaporated in the RAM air supply to the secondary heat exchanger. A dehumidified air moves from the water extractor and into a turbine. An expanded air from the turbine flows through the condenser in the capacity as a coolant medium. When the air flow from the condenser passes through a liquid-o-air heat exchanger, a relatively warmer liquid from a liquid loop is cooled and then used to cool avionics. After the air flow moves through the liquid-to-air heat exchanger, the flow becomes the supply to the cabin.
Although providing advantages, the above conventional ACCS with a liquid loop has also presented disadvantages. For example, the air-to-air heat exchangers are relatively bulky and, thus, do not make the most efficient use of space. Of course, with less bulkier components, greater cooling capacity can be achieved with a given amount of space. If the ACCS is used as a retrofit, a bulkier system size means fewer opportunities for the ACCS to fit into different spaces to be retrofitted. Also, the liquid load is typically rejected directly into the cooling air supply. That means the ACCS will have to be increased in size to accommodate the load.
As can be seen, there is a need for an ACCS with a liquid loop that is small in size such that for a given space a greater cooling capacity can be achieved. There is also a need for an ACCS which, due to its relatively small size, can serve as a retrofit in more environments. Further, an ACCS is needed which can more efficiently utilize a liquid loop by also using it during the water vapor removal process of the air to be conditioned.